How Will Global Warming and Climate Change Impact the Wine World?

By Special Wine Columnist, Richard Olsen-Harbich

Will it be a brave new wine world?

During the past year, discussions about the potential impact of “global warming” have dominated the mass media. Although the exact outcomes and causes are in dispute, few now doubt the existence of the phenomenon. What does it mean for the wine industry? As wine is all about long-term agriculture and entirely dependant on the weather, I’d say a great deal.

The eventual consequences of climate change on the wine industry are unclear, as are the possible effects on the rest of the planet. The real question is: Are the changes something we will only see in the distant future or are they something we’re living and breathing right at this moment?

When I was a graduate student in science education at Stony Brook in the late 1980s, I did my Masters thesis on climate change and the potential effects on Long Island. At the time, the concept was little more than a derided footnote in the public consciousness. However—even back then—the research was clear that climate change was real.

I particularly remember conversations I had with Dr. Anthony D. Del Genio at the NASA Goddard Institute for Space Studies (GISS) at Columbia University. Dr. Del Genio is a planetary physicist who has been studying climate models since the 1970s. He is also a wine buff and had done some investigation of his own into the effects of climate change on the wine industry. Most importantly, I remember when he told me, “All of us will begin to feel the effects of climate change by the end of the 1990s.” He not only was prescient—he also had some really good data.

One of the main tools used to track climate in agriculture is Growing Degree Days or GDD. This is a system that cumulatively calculates the average daily temperature of the growing season using a base of 50 degrees F. Winegrowers have used this system for many years to determine the boundaries of local climate as well as helping predict the quality and timing of the vintage. Cooler regions have fewer GDD and warmer regions have higher GDD. I’ve listed some examples of GDD as described in the seminal textbook General Viticulture by A.J. Winkler, published in 1974:

I        < 2500           (Geisenheim, Germany, Geneva, NY)   
II       2501-3000    (Napa, CA, Bridgehampton, L.I.)
III     3001-3500    (Oakville, CA, Riverhead,  L.I.)
IV     3501-4000    (Lodi, CA, Sidney, AU)
V      4001              (Fresno, CA, Tehran, Iran)

I decided to look at some more recent data from the past 20 years and see if anything new turned up. For one, Northern California is becoming much warmer. The city of Napa, which used to be classified as a Region II back in the 1970s, is now averaging seasons that are well into Region III and often as high as Region IV. Other areas within Napa Valley and Sonoma have reached well over 4000 GDD in past 5 years—approaching conditions that might make it difficult to produce quality wines in the near future.

Back East, things get a little more complicated. Data obtained for the Finger Lakes region since the 1970s show no statistically significant increase in GDD. It is surprisingly consistent, with average GDD hovering around 2600 for most areas around the lakes.

Long Island presents an entirely different story. When I first wrote and
applied for the 2 local AVAs – The Hampton’s, L.I. in 1984 and The
North Fork of Long Island in 1985, I used data that went back to the
1940s. According to that information, the North Fork (represented by
Riverhead data) had an average of 2932 GDD while the Hampton’s,
(represented by Bridgehampton data) averaged 2531 GDD. Over the past 11
years, the numbers look quite different. Since 1996, the average GDD
for Riverhead is 3331 days, while the average for Bridgehampton is 2805
– an increase of 399 and 274 respectively for these two regions.
Although it is not a long enough period of time to draw a definitive
conclusion, one can definitely see the trend; on Long Island as well as
in California, an average increase of 300-500 GDD has been recorded
since the 1970s.

This summer I contacted Dr. Del Genio again and mentioned to him I was
going to write a piece revisiting this topic. I also wanted to get his
thoughts on what has changed in his understanding since 1990 and what
he sees in the future. Interestingly, he mentioned that he and his
staff have begun to draw some new conclusions from the models used to
predict climate change. He stated that since the onset of Clean Air
Legislation that began in the 1960s, the levels of particulates (i.e.
dust, soot, etc.) in the air have decreased, which ironically, has lead
to higher recorded temperatures in the densely populated areas of the
Northeast, Midwest and California. These particles in the air known as
aerosols scatter sunlight and make the light less concentrated—in
essence, masking the warming effects of elevated CO2 levels.

The areas showing the greatest response to clean air legislation are
showing the greatest rise in temperature today—as much as 2-3 degrees F
on average. This effect is seen on Long Island since we are close to
NYC—but he also mentioned our maritime influence, which is so important
for moderating winter temperatures. Our reduced aerosols—along with
slight increases in water temperature—are more than likely responsible
for the increase in GDD. It also explains why a region like the Finger
Lakes, further removed from air quality issues and with more of a
continental climate, is presently showing less of a warming effect.
This is one good example of just how complex a system our climate is
and why it is so hard to accurately determine future outcomes.

As for the future, Dr. Del Genio stated that new climate models predict
we will experience increases of anywhere from 400-500 GDD over
historical averages, by end of the next decade. I mentioned to him that
I had run the numbers and saw this beginning to happen. He was not
surprised; again, Dr. Del Genio was on the money. When I asked him what
stocks he would recommend though, he said he was only a physicist.

To ignore the influence of climate change with regard to wine growing
would be a mistake. When or how we will deal with these issues in our
lifetime is another matter, but I believe we are beginning to. In last
five years, we’ve experienced years that were the warmest on record,
(2002) the warm and perpetually overcast (2003) and the extreme hot and
dry followed by rains of biblical proportions (2005). Clearly, many in
California are addressing the issue today, seen by the numerous land
purchases by wineries and viticultural speculators in the cooler areas
of the Northwest.

In the future, a warmer climate may mean many things. On the positive
side it may extend the length of growing season and allow us the
ability to plant later-ripening varieties. It may even open up entirely
new regions for viticulture in areas where vines have not been
successful before.

Conversely, warmer climate might mean the dilution and disappearance of
terroir in certain regions as well as some traditional wine styles we
are familiar with—particularly those in the cooler wine producing
regions of Europe. Dr. Robert Pincus, a climatologist at the NOAA in
Colorado who has written extensively about the wine industry, states in
the journal Gastronomica, that “in an increasingly warm world, the
particular associations between wine and place will be difficult or
impossible to maintain.” His studies led him to conclude that “even
where the impact of climate change is less dramatic, decades, even
centuries of viticultural experience will be rendered irrelevant.”
Aside from higher temperatures, climate models predict changes in the
levels and rates of precipitation and most importantly for Long Island,
stronger and more frequent hurricanes, which could make life a little
more precarious for everyone—winegrowers included.
The term we need to be using is not global warming—but climate change.
As the name states, climate change is just that. It’s not only about
warming, its about a change in a complex system that we still do not
fully understand that could include a broad set of possibilities.

One thing is certain—winegrowers have always learned to adapt and will
certainly do so in the future—experimenting with novel varieties,
defining new terroir and developing unique wine styles. Perhaps we
don’t know yet exactly what all those changes will turn out to be, but
something tells me we’ll be much better off if we could listen more
closely to people like Dr. Tony DelGenio.